paintComponent 方法不起作用 - Java

Posted 2023-03-27

【中文标题】paintComponent 方法不起作用 - Java

【英文标题】：paintComponent method won't work - Java

【发布时间】：2016-02-09 10:39:46

【问题描述】：

当我使用此代码时，我的屏幕将为空。所以这意味着 我的paintComponent 方法有问题。但是有什么问题呢？我该如何解决？我的预期输出是一个深灰色的矩形和一个图像。

代码：

package _47b3n.seg.main.engine;

import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import javax.swing.ImageIcon;
import javax.swing.JPanel;
import _47b3n.seg.main.frame.Frame;

public class Engine extends JPanel 

public int xOff;
public int yOff;
public int x;
public int y;
public int fpsInt = 199;

public boolean isRunning = true;

public FPS fps = new FPS();

public static void main(String [] args) 
    Frame frame = new Frame();
    frame.setFrame(800, 600, "Super easy game", "0.0.1");
    new Engine();


public Engine() 
    start();


public void move() 
    x+=xOff;
    y+=yOff;


public void start() 
    Thread loop = new Thread () 
        public void run() 
            gameLoop();
            addKeyListener(new keyInput());
        
    ;
    loop.start();



public void paintComponent(Graphics g) 
    super.paintComponent(g);
    g.setColor(Color.DARK_GRAY);
    g.fillRect(10, 10, 10, 10);
    g.drawImage(new ImageIcon("Poppetje.jpg").getImage(), x, y, null);


public void gameLoop() 
    while(isRunning) 
        move();
        repaint();
        fps.update();
        fpsInt++;
        if (fpsInt == 200) 
            System.out.println("[Console] " + fps.getFPS() + " FPS");
            fpsInt = 0;
        
        try Thread.sleep(17); catch (InterruptedException e) e.printStackTrace();
    
   

public class keyInput extends KeyAdapter 

    public void keyPressed(KeyEvent e) 
        int key = e.getKeyCode();

        if(key == KeyEvent.VK_W) 
            yOff = -1;
        

        if (key == KeyEvent.VK_S) 
            yOff = 1;
        

        if (key == KeyEvent.VK_A) 
            yOff = -1;
        

        if (key == KeyEvent.VK_D) 
            xOff = 1;
        
    

    public void keyReleased(KeyEvent e) 
        int key = e.getKeyCode();


        if (key == KeyEvent.VK_W) 
            yOff = 0;

        

        if (key == KeyEvent.VK_S) 
            yOff = 0;
        

        if (key == KeyEvent.VK_A) 
            xOff = 0;
        

        if (key == KeyEvent.VK_D) 
            xOff = 0;
        

    

谢谢

【参考方案1】：

不知道这是否是唯一的问题，但您从未将面板添加到框架中：

//new Engine();
Engine engine = new Engine();
frame.add(engine);
frame.setVisible(true);